Simon Ussher

Simon Ussher
University of Plymouth | UoP · Biogeochemistry and Environmental Analytical Chemistry (BEACh) group

About

64
Publications
6,428
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2,098
Citations
Citations since 2016
21 Research Items
997 Citations
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150

Publications

Publications (64)
Article
We used a combined ion pairing - organic matter speciation model (NICA-Donnan) to predict the organic complexation of iron (Fe) at ambient pH and temperature in the Celtic Sea. We optimized our model by direct comparison with Fe speciation determined by Adsorptive Cathodic Stripping Voltammetry using the added Fe-binding ligand 1-nitroso-2-naphthol...
Article
Dry deposition of nitrogen (N) and phosphorus (P) from the aerosol phase represents a potential source of nutrients to marine surface waters. To investigate the significance of this deposition pathway, aerosol samples were collected from Penlee Point Atmospheric Observatory in SW England, UK, over a 6-month period (February to July 2015) covering t...
Article
Full-text available
In order to investigate the pollution characteristics of size-segregated particles and metal elements (MEs) after the Chinese Air Pollution Prevention Action Plan was released in 2013, an intensive field campaign was conducted in the suburban area of Chaoyang District, Beijing in winter 2016. The size distributions of particle mass concentrations w...
Chapter
Shipping is responsible for transporting 90% of the world's trade. This book provides a comprehensive review of the impact shipping has on the environment. Topics covered include pollutant discharges such as atmospheric emissions, oil, chemical waste, sewage and biocides; as well as non-pollutant impacts including invasive species, wildlife collisi...
Article
Dimethyl sulfide (DMS) is the major biogenic volatile sulfur compound in surface seawater. Good quality DMS data with high temporal and spatial resolution is desirable for understanding reduced sulfur biogeochemistry. Here we present a fully automated and novel “microslug” gas-liquid segmented flow-chemiluminescence (MSSF-CL) based method for the c...
Article
Full-text available
Continental margins are disproportionally important for global primary production, fisheries and CO 2 uptake. However, across the Northeast Atlantic shelves, there has been an ongoing summertime decline of key biota-large diatoms, dinoflagellates and copepods-that traditionally fuel higher tropic levels such as fish, sea birds and marine mammals. H...
Article
Water-column data from seven cruises in 2007–2008 reveal pronounced temporal and spatial variations in the distribution of dissolved iron (DFe, <0.4 μm) over the upper 1000 m of the Sargasso Sea near Bermuda, in the western subtropical North Atlantic Ocean. In near-surface waters, DFe exhibits a clear seasonal cycle, increasing from ~0.1–0.3 nM in...
Article
Accurate and precise measurements of marine macronutrient concentrations are fundamental to our understanding of biogeochemical cycles in the ocean. Quantifying the measurement uncertainty associated with macronutrient measurements remains a challenge. Large systematic biases (up to 10%) have been identified between datasets, restricting the abilit...
Article
Full-text available
The availability of iron (Fe) can seasonally limit phytoplankton growth in the High Latitude North Atlantic (HLNA), greatly reducing the efficiency of the biological carbon pump. However, the spatial extent of seasonal iron limitation is not yet known. We present autumn nutrient and dissolved Fe measurements, combined with microphytoplankton distri...
Article
High quality observational data with a firm uncertainty assessment are essential for the proper validation of biogeochemical models for trace metals such as iron. Typically, concentrations of these metals are very low in oceanic waters (nM and sub nM) and ICP-MS is therefore a favoured technique for quantitative analysis. Uncertainties in the measu...
Article
Full-text available
A realistic estimation of uncertainty is an essential requirement for all analytical measurements. It is common practice, however, for the uncertainty estimate of a chemical measurement to be based on the instrumental precision associated with the analysis of a single or multiple samples, which can lead to underestimation. Within the context of che...
Article
Full-text available
The fractional solubility of aerosol-derived trace elements deposited to the ocean surface is a key parameter of many marine biogeochemical models. Despite this, it is currently poorly constrained, in part due to the complex interplay between the various processes that govern the solubilisation of aerosol trace elements. In this study, we used a se...
Article
Full-text available
Anthropogenic activities have resulted in enhanced lead (Pb) emissions to the environment over the past century, mainly through the combustion of leaded gasoline. Here, we present the first combined dissolved (DPb), labile (LpPb) and particulate (PPb) Pb dataset from the Northeast Atlantic (Celtic Sea) since the phasing out of leaded gasoline in Eu...
Article
Full-text available
The fractional solubility of aerosol-derived trace elements deposited to the ocean surface is a key parameter of many marine biogeochemical models. Yet, it is currently poorly constrained, in part due to the complex interplay between the various processes that govern the solubilisation of aerosol trace elements. In this study, we used a sequential...
Article
Atmospheric deposition is an important pathway by which bioactive trace metals are delivered to the surface ocean. The proportions of total aerosol trace metals that dissolve in seawater, and thus become available to biota, are not well constrained and are therefore a key uncertainty when estimating atmospheric fluxes of these elements to surface w...
Article
Full-text available
Our study followed the seasonal cycling of soluble (SFe), colloidal (CFe), dissolved (DFe), total dissolvable (TDFe), labile particulate (LPFe) and total particulate (TPFe) iron in the Celtic Sea (NE Atlantic Ocean). Preferential uptake of SFe occurred during the spring bloom, preceding the removal of CFe. Uptake and export of Fe during the spring...
Article
Full-text available
This work assesses the components contributing to the combined uncertainty budget associated with the measurement of the Fe amount content by flow injection chemiluminescence (FI-CL) in <0.2 μm filtered and acidified seawater samples. Amounts of loaded standard solutions and samples were determined gravimetrically by differential weighing. Up to 5%...
Article
This paper overviews the evolution of suitable analytical approaches for the determination of dissolved iron in seawater. The focus is on sampling and sample treatment, detection methods and quality assurance of the data. Iron is a vital trace element for the growth of marine organisms and is the limiting micronutrient for primary production in man...
Article
The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the...
Article
[1] Dissolved iron (dFe) distributions and atmospheric and vertical subduction fluxes of dFe were determined in the upper water column for two meridional transects of the Atlantic Ocean. The data demonstrate the disparity between the iron biogeochemistry of the North and South Atlantic Ocean and show well-defined gradients of size fractionated iron...
Article
A study was carried out to assess primary production and associated export flux in the coastal waters of the western Antarctic Peninsula at an oceanographic time-series site. New, i.e., exportable, primary production in the upper water-column was estimated in two ways; by nutrient deficit measurements, and by primary production rate measurements us...
Article
The first large-scale international intercomparison of analytical methods for the determination of dissolved iron in seawater was carried out between October 2000 and December 2002. The exercise was conducted as a rigorously “blind” comparison of 7 analytical techniques by 24 international laboratories. The comparison was based on a large volume (7...
Article
Full-text available
Dissolved cobalt (dCo), iron (dFe) and aluminum (dAl) were determined in water column samples along a meridional transect (∼31°N to 24°N) south of Bermuda in June 2008. A general north-to-south increase in surface concentrations of dFe (0.3–1.6 nM) and dAl (14–42 nM) was observed, suggesting that aerosol deposition is a significant source of dFe an...
Article
Previous measurements of the benthic nitrogen (N) flux from resuspended estuarine particles in the Thames Estuary appeared to underestimate benthic inputs. This study attempted to address experimental limitations by using a mini-annular flume. The flume has a 45l capacity and was prepared in order to facilitate trace chemical analysis of N. Sedimen...
Article
We report seawater dissolution experiments for aerosol samples simultaneously collected (October 2007) across the Levantine Basin (LB, Eastern Mediterranean Sea), a marine system influenced by seasonal atmospheric inputs. Two distinct populations exhibited contrasting kinetic profiles; those representative of strong Saharan dust events which had va...
Article
The distribution of size fractionated dissolved iron (DFe, <0.2 mum) species was determined in the upper water column (0-150 m) of the Canary Basin (25-32 degrees N and 18-24 degrees W) on a research cruise in October 2002. A DFe concentration gradient resulting from a decrease in both soluble iron (SFe, <0.02 microm) and colloidal iron (CFe, 0.02-...
Article
Environmental context. The importance of iron as a limiting micronutrient for primary production in the marine environment and its complex marine biogeochemical cycle necessitate accurate methods for the determination of iron in seawater. Current analytical challenges include the detection of trace concentrations (sub-nanomolar) and the high potent...
Article
Full-text available
Oceanic fixed-nitrogen concentrations are controlled by the balance between nitrogen fixation and denitrification1–4. A number of factors, including iron limitation5–7, can restrict nitrogen fixation, introducing the potential for decoupling of nitrogen inputs and losses2,5,8. Such decoupling could significantly affect the oceanic fixed-nitrogen in...
Article
A detailed investigation into the performance of two flow injection-chemiluminescence (FI-CL) manifolds (with and without a preconcentration column) for the determination of sub-nanomolar dissolved iron (Fe(II)+Fe(III)), following the reduction of Fe(III) by sulphite, in seawater is described. Kinetic experiments were conducted to examine the effic...
Article
Siderophores are chelates produced by bacteria as part of a highly specific iron uptake mechanism. They are thought to be important in the bacterial acquisition of iron in seawater and to influence iron biogeochemistry in the ocean. We have identified and quantified two types of siderophores in seawater samples collected from the Atlantic Ocean. Th...
Article
Data from 6 cruises in 2007-2008 and 3 cruises in 2003-2004 reveal a remarkable temporal and spatial variability in the distribution of dissolved iron (DFe,
Article
Full-text available
An automatic sampler for natural waters under LabVIEW control is described. The sampler was integrated with an incubation system and coupled with a flow injection chemiluminescence detection system to study the dissolution of aerosol iron in seawater at environmentally relevant concentrations. Automated sampling of seawater was achieved using a per...
Article
To investigate the biogeochemistry of iron in the waters of the European continental margin, we determined the dissolved iron distribution and redox speciation in filtered (,0.2 mm) open-ocean and shelf waters. Depth profiles were sampled over the shelf slope southeast of the Chapelle Bank area (47.61uN, 4.24uW to 46.00uN, 8.01uW) and a horizontal...
Article
Aerosol (soluble and total) iron and water-column dissolved (DFe, < 0.2 μm) and total dissolvable (TDFe, unfiltered) iron concentrations were determined in the Canary Basin and along a transect towards the Strait of Gibraltar, in order to sample across the Saharan dust plume. Cumulative dust deposition fluxes estimated from direct aerosol sampling...
Article
Environmental context. Iron is arguably the most important trace element for the growth of marine organisms and is the limiting micronutrient for primary production in many parts of the world’s oceans. The concentration of dissolved iron in seawater therefore influences the global carbon cycle and consequently Earth’s climate. Hence, it is importan...
Article
Dissolved iron (DFe; <0.2µm) and dissolved manganese (DMn; <0.2µm) concentrations were determined in the water column of the Bay of Biscay (eastern North Atlantic Ocean) in March 2002. The samples were collected along a transect traversing from the European continental shelf over the continental slope. The highest DFe and DMn concentrations (2.39nM...
Article
To investigate the biogeochemistry of iron in the waters of the European continental margin, we determined the dissolved iron distribution and redox speciation in filtered (,0.2 mm) open-ocean and shelf waters. Depth profiles were sampled over the shelf slope southeast of the Chapelle Bank area (47.61uN, 4.24uW to 46.00uN, 8.01uW) and a horizontal...
Article
Full-text available
Dissolved iron (DFe; <0.2 µm) and dissolved manganese (DMn; <0.2 µm) concentrations were determined in the water column of the Bay of Biscay (eastern North Atlantic Ocean) in March 2002. The samples were collected along a transect traversing from the European continental shelf over the continental slope. The highest DFe and DMn concentrations (2.39...
Article
Full-text available
Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 19 (2005): GB4006, doi:10.1029/2004GB002445. We report iron measurements for water column and aerosol samples colle...
Article
The effects of dissolved organic compounds on the determination of nanomolar concentrations of Fe(II) have been compared using two luminol-based flow injection chemiluminescence (FI-CL) methods. One used the direct injection of sample into the luminol reagent stream, and the other incorporated on-line solid-phase extraction of the analyte on an 8-h...
Article
Full-text available
A flow-injection (FI)-based instrument under LabVIEW control for monitoring iron in marine waters is described. The instrument incorporates a miniature, low-power photomultiplier tube (PMT), and a number of microelectric and solenoid actuated valves and peristaltic pumps. The software allows full control of all flow injection components and process...
Data
We report iron measurements for water column and aerosol samples collected in the Sargasso Sea during July-August 2003 (summer 2003) and April-May 2004 (spring 2004). Our data reveal a large seasonal change in the dissolved iron (dFe) concentration of surface waters in the Bermuda Atlantic Time-series Study region, from ~1-2 nM in summer 2003, when...
Article
Siderophore type chelates were isolated from nutrient enriched seawater collected from coastal and near shore environments and detected using a novel high performance liquid chromatography–electrospray ionisation–mass spectrometric technique. Seawater was enriched with added glucose, ammonia and phosphate, and incubated for four days. Seven differe...
Article
Environmental Context. Several trace elements are essential to the growth of microorganisms, iron being arguably the most important. Marine microorganisms, which affect the global carbon cycle and consequently indirectly influence the world’s climate, are therefore sensitive to the presence of iron. This link means iron-related oceanic processes ar...
Article
Dissolved iron ( 0.8 nM) generally found in the shallow shelf waters. These observations imply that benthic inputs and sediment resuspension may form important inputs of dissolved iron and iron(II) in the shelf waters. Iron speciation measurements were also made for underway surface and shallow cast samples during the Iron from Above cruise October...
Article
In order to better understand the atmospheric delivery of Fe and its impact on the Fe distribution in the water column, we investigated the distribution of total dissolved (filtered samples, 0.2 mum) Fe (DFe) in the Canary basin, a region subjected to high atmospheric inputs especially from Saharan origin. Samples were collected from a fish towed f...
Article
Reliable protocols for determining dissolved iron (DFe) at picomolar concentrations in seawater (including sample and sample treatment) are essential for the provision of high quality analytical data. This is needed to distinguish between real environmental variability and analytical performance and to compare oceanic iron data with different spati...
Article
A shipboard-deployable, flow-injection (FI) based instrument for monitoring iron(II) in surface marine waters is described. It incorporates a miniature, low-power photon-counting head for measuring the light emitted from the iron(II)-catalyzed chemiluminescence (CL) luminol reaction. System control, signal acquisition, and data processing are perfo...
Article
This article describes the use of flow-injection techniques combined with molecular spectroscopic detection (spectrophotometry, fluorescence and chemiluminescence) for the rapid determination of chemical parameters in environmental matrices. The emphasis is on field deployment in order to obtain high temporal and spatial resolution data without the...
Article
Historical measurements of "dissolved" iron in open-ocean seawater have been operationally defined as the fraction of iron which passes through a 0.4 mum (or 0.2 mum) pore membrane filter. As such, these measurements are likely to include iron(III) and iron(II), both free and complexed by a variety of organic and inorganic ligands, as well as collo...

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